The needle jet or the main jet?

It seems to me that the needle jet would be most important since it controls the larger throttle range and it's the range you're most likely to spend the most amount of time in (provided you are a trail rider)....

So why all the fuss about the main jet? Simply because most people don't know any better or they are only concerned with top speed or it's the best tuning jet? Or is it because it's generally easier to change than anything else? [img]i/expressions/face-icon-small-wink.gif[/img]

And when doing plug checks, do you use new plugs for each throttle position? Is it essential that you run it under load? Do you start with the bottom end of the throttle checks and work your way up or is it better to work your way down?

I'm not doing any changes yet but I am trying to get more info and trying to clear the air about jetting.....thanks for any info! [img]i/expressions/face-icon-small-smile.gif[/img]

 

You did'nt say for what type of carb,CV,PUMPER,TB ECT.

later

 

I didn't think that mattered all that much since the internal workings for moto/atv carbs are basically the same in principle...2 stroke or 4 stroke.

In doing some searching I found this great article: Carburetor Tuning

Here's another I've had for a while: Carb101

Another: Carb

Even after reading all this I still don't really know and don't have any real world experience......thus my question here...

 

Hey Rook, to tell you the truth, for us with the 500 scrams, it is actually easier to change the needle jet rather than the main jet. The main jet you need to remove the carb, drain the gas, and rotate it so you can take the jet out from the bottom. Then crank on it for a while to get it started afterward. With the needle jet, you just remove the top of the carb and the spring and diaphram and the needle jet is right there. No need to remove the carb. Just some useful info.